Mobile devices, such as smart phones, are carried by a user throughout most or all of a day. These devices include the capability of playing music, videos, or other audio through headphones. Users often take advantage of having a source of music available throughout the day. For example, users often walk along the streets, ride bicycles, or ride motorized vehicles with headphones around their ears or headphone earbuds inserted in their ears. The use of the headphones impairs the user's ability to receive audible clues about the environment around them. For example, a user may be unable to hear the siren of an emergency vehicle while wearing the headphones with audio playing from the mobile device.
In addition to the physical impairment to audible sounds created by a user wearing the headphones, the mobile device and/or the headphones may implement noise cancellation. With noise cancellation, a microphone near the mobile device or headphones is used to detect sounds in the surrounding environment and intentionally subtract the sounds from what the user hears. Thus, when noise cancellation is active, the user only hears the audio from the device. For example, the mobile device or headphones may generate a signal that is out-of-phase with the sounds and add the out-of-phase signal to the music played through the headphones. Thus, when the environmental sound reaches the user's ear, the cancellation signal added to the music offsets the environmental sound and the user does not hear the environment. When the audible sound is the siren of an emergency vehicle, the user may be unaware of an emergency around him or may be unaware of an approaching high speed vehicle. This has become a particularly dangerous situation as noise cancellation in headphones has improved.
One conventional solution is for the mobile device to detect certain sounds, such as an emergency siren through the microphone and mute the audio output through the headphones while particular sounds are detected. However, this solution requires advance knowledge of each of the sounds. For example, a database of all emergency sirens would need to be created and updated regularly in order to recognize all emergency vehicles. Furthermore, the input from the microphone is noisy and the emergency siren may be covered by other nearby audible sounds, such as nearby car engines, generators, wildlife, etc. Thus, audibly detecting warning sounds may be difficult, and mute functionality based on audible detection of sounds may not be reliable.
Shortcomings mentioned here are only representative and are included simply to highlight that a need exists for improved audio devices and headphones, particularly for consumer-level devices. Embodiments described here address certain shortcomings but not necessarily each and every one described here or known in the art.